19315-ZY9-H01 Thermostat Cover - Overview. The 19315-ZY9-H01 Thermostat Cover is a crucial component in Honda marine engine systems. This cover protects the thermostat, which helps regulate engine temperature, ensuring your marine engine operates efficiently and reliably. By enclosing the thermostat, it safeguards against contaminants and physical damage, maintaining the engine's cooling system integrity. Designed for Honda Marine engines, it ensures seamless integration with existing parts, mai